Radiation therapy for cancer gets on the beam

Radiation therapy, a treatment for cancer more than a century
old, has become much more powerful and precise with the help of the
computer. Harmful side effects of radiation on normal tissue have
been lessened, and tumors once untreatable by radiation can now be
reached.

Two relatively new technologies, called the CyberKnife and
intensity modulated radiation therapy (IMRT) , make plentiful use
of computing power and precise medical imaging to determine the
tumor location. The details of how they work are different, but
both deliver X-ray radiation in a concentrated pattern from many
directions that converge at the tumor.

The concept resembles that of another targeted radiation
therapy, called the Gamma Knife, which sends about 200 beams of
gamma radiation into the tumor. But while the Gamma Knife can be
used only for lesions of the brain, the CyberKnife and IMRT can be
used over the entire body.

IMRT and the CyberKnife are "complementary," said Cihat
Ozhasoglu, a medical physicist at the University of Pittsburgh
Medical Center. The CyberKnife, the newer of the two therapies, is
more precise in delivering radiation. But IMRT is superior for
treating large and irregular tumors.

Because radiation damage to normal tissue is lessened, both
treatments cause less fatigue in patients, a common side effect of
radiation, than in conventional radiation.

"It's much more pleasant than I thought it would be," said
Eugene Fundum, a Temecula resident who received IMRT for prostate
cancer. Fundum, 76, was treated at the Vantage Oncology Redhawk
Radiation Therapy Center, which opened earlier this year in
Temecula.

Earle Grueskin took CyberKnife therapy at the San Diego
CyberKnife center in Kearny Mesa. Grueskin is also 76 and also has
prostate cancer.

"There was absolutely no pain before, during or after the
treatments," Grueskin said.

Both Fundum and Grueskin said their levels of PSA (prostate
specific antigen, an indicator for prostate cancer), have declined
dramatically since their treatment in July. They'll need periodic
checkups to check for tumor regrowth.

IMRT

The name gives a good indication of how intensity modulated
radiation therapy works. It delivers patterns of radiation that
vary in intensity. That's important because certain parts of the
body are more sensitive to radiation than others. The prostate, for
example, is located between the bladder and rectum. Radiation to
these organs must be controlled to avoid damaging bladder and bowel
function.

First, the patient is given a CT scan to map the area, so the
staff can plan the treatment. A CT scan is a series of X-rays, each
focused to show a sharp image of adjacent thin slices of the area.
These are digitally combined in a computer to form a 3-D image.
This shows where the tumor is in the patient.

That's not enough, however. The patient's position must be
tracked so if he or she moves, the radiation's path also moves. An
ultrasound guidance system called SonArray provides that
information, said Mary Ann Rose, M.D., a radiation oncologist who
is medical director of Redhawk Radiation Therapy Center and
Wildomar Radiation Therapy Center. The centers, owned by Vantage
Oncology, provide a variety of other radiation therapies.